Catalogue services support the ability to publish and search collections of descriptive information metadata for data, services, and related information objects. Metadata in
catalogues represent resource characteristics that can be queried and presented for evaluation and further processing by both humans and software. Catalogue services are
required to support the discovery and binding to registered information resources within an information community.
The OpenGIS
®
catalog document specifies the interfaces, bindings, and a framework for defining application profiles required to publish and access digital catalogues of metadata
for geospatial content, services, and related resource information. Metadata act as generalized properties that can be queried and returned through catalogue services for
resource evaluation and, in many cases, invocation or retrieval of the referenced resource. Catalogue services support the use of one of several identified query languages to find and
return results using well-known content models metadata schemas and encodings. This OpenGIS
®
document is applicable to the implementation of interfaces on catalogues of a variety of information resources.
3.5 Data Services
Data Services provide access to collections of content in repositories and databases. Resources accessible by Data Services can generally be referenced by a name identity,
address, etc. Given a name, Data Services can then find the resource. Data Services usually maintain indexes to help speed up the process of finding items by name or by other
attributes of the item. The OpenGIS Framework defines common encodings and interfaces in which multiple, distributed Data Services are accessed and their contents “exposed” in a
consistent manner to other major components. The sections below describe the current set of Data Services of the OpenGIS Framework.
3.5.1 Feature Services
The OpenGIS Web Feature Service Specification
8
WFS supports the query and discovery of geographic features and attributes. In a typical Web-base scenario, WFS delivers
Geography Markup Language
9
GML representations of simple geospatial features in response to queries from HTTP clients. Clients service requestors access geographic
feature data through a WFS by submitting a request for just those features that are needed for an application. The client generates a request posts it to a WFS instance a WFS server
on the Web. The WFS instance executes the request, returning the results to the client as GML. A GML-enabled client can manipulate or operate on the returned features.
3.5.2 Symbology Management
This service is a multi-component system that enables map and content retrieval, and includes the capability for creating, storing, andor retrieving styles and symbols from
multiple communities or user groups and combining all these elements of information into
OGC 2004 – All rights reserved
8
https:portal.opengeospatial.orgfiles?artifact_id=7176
9
https:portal.opengeospatial.orgfiles?artifact_id=7174
14
©
